Crystal facets engineering and rGO hybridizing for synergistic enhancement of photocatalytic activity of nickel disulfide

Crystal facets engineering and graphene hybridizing for the synergistic enhancement of photocatalytic activity of nickel disulfide were demonstrated. [Display omitted] •NiS2 nanocrystals with specific crystal facets were prepared.•The faceted NiS2 nanocrystals were hybridized with rGO nanosheets.•Strong crystal facets effect in photocatalytic degradation was demonstrated.•The photocatalytic activity was further enhanced by rGO hybridizing.•The photocatalytic mechanism was studied by first-principles calculation. Crystal facets engineering and graphene hybridizing have been proved to be effective means to improve the photocatalytic activities of semiconductor photocatalysts in recent years. However, most of these efforts are concentrated in metal oxides. In the present study, crystal facets effect on the photocatalytic activity of metal sulfide NiS2 was studied for the first time. It was found that the {111}-faceted NiS2 nanocrystals showed improved photocatalytic activity in the degradation of various typical pollutants in water compared with {100}-faceted NiS2 nanocrystals. Moreover, through hybridizing with rGO nanosheets, the photocatalytic activity of the {111}-faceted NiS2 nanocrystals can be further improved, resulting in the complete degradation of heavy metal hexavalent chromium and organic dyes. The photocatalytic mechanism was studied in detail through theory calculation and experimental characterization. It was found that both the surface energies of Ni-terminated and S-terminated {111} facets were much higher than that of {100} facets, indicating that {111} facets were more active. Besides, rGO hybridizing can realize the effective separation of photogenerated electrons and holes. The results provide important guidance for the further development of efficient metal sulfide photocatalysts.